Interactions between typhoons Parma and Melor (2009) in North West Pacific Ocean

Abstract

This paper analyzes the interactions between typhoons (TYs) Parma and Melor (2009) in the North West Pacific (NWP) Ocean. The TY Parma (2009) is chosen for investigation because it has a unique track with multiple U-turns and 3 landfalls over the Luzan Island of Philippines that are extremely difficult, if not impossible, to forecast by numerical weather prediction models due to which it caused 500 fatalities and an estimated economical loss up to 581 million USD. Its diagnostic analysis becomes readily convenient by using the Liou-Liu empirical formulas that were recently developed for examining the Fujiwhara effect. The analysis leads to recognitions of all different types of Fujiwhara effect that occurred between TYs Parma and Melor along with detection and verification of the time of strong interaction. Comparison with historical TYs of the NWP region is also conducted to verify the existence of Fujiwhara effect in the Parma-Melor interaction case. It is concluded that three types of Fujiwhara interactions are identified, namely elastic interaction (EI) on 3, 4, and 8 October, partial merger (PM) on 6 October, and partial straining-out (PSO) on 7 October 2009. The role of cirrus clouds in identifying the interaction between TYs is found crucial. The Liou-Liu empirical formulas are found capable of detecting the time of strong Fujiwhara interaction between the two TYs of concern (06 UTC on 06 October 2009). The time of strong interaction is further verified by the 24-hr noticeably sharp variation in central pressure percentage and 10-min maximum sustained wind percentage in both TYs, accompanied by a backward track movement of the TY Parma. In addition, the analysis reveals that during the time of strong interaction, the weaker TY Parma was partially strengthened by stronger TY Melor. Comparison of TY Parma with the other similar TYs from the past reveals that typical TYs without interaction do not move southwards (backwards) or stagnate longer on the Luzon Island of the Philippines after once they do landfall. This kind of research is crucial for mitigating the impact of dual-TYs interaction in the NWP Ocean.